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LAST NEURO EVER > BG > Flashcards

BG Flashcards

1
Q

What are the structures of the basal ganglia?

A

-structures that yield distinctive kinds of mvmd disorders when damaged:

Striatum
-caudate + putamen

Globus pallidus
-interna and externa

sub thalamic nucleus

substantia nigra
-compact and reticular parts

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2
Q

What is the major outflow pathway to the thalamus from the BG?

A

globus pallidus

reticular substantia nigra (less so)

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3
Q

What are the general features of BG related mvmt disorders?

A

involuntary movements, hyperkinetic disorders (chorea, athetosis, ballismus)

difficulty initiating mvmt

general increase in flexor/extensor tone, can cause rigidity and abnormal fixed posture (dystonia)

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4
Q

What are the two main diseases discussed in relation to the BG?

A

huntington’s and parkinson’s

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5
Q

What degrades when you have huntingtons?

A

stratum (caudate and putamen)

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6
Q

What are the two outflow pathways of the globus pallidus?

A

ansa lenticularis

lenticular fasciculus

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7
Q

What are the two parts of the substantia nigra and what do they do?

A

compact part: sends dopaminergic projections to striatum

reticular part: basal ganglia output nucleus

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8
Q

What are the four basic circuits of the basal ganglia?

A

motor loop: learned mvmts

cognitive loop: motor intentions

limbic loop: emotional aspects of mvmt

oculomotor loop: voluntary saccades

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9
Q

Can the basal ganglia initiate mvmts?

A

NO but it is active during all mvmts

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10
Q

What does the BG motor loop do?

A

influences descending motor pathways by scaling strength of muscle contractions, organizes order of mvmts needed with the supplemental motor area.

mostly involves putamen

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11
Q

What does the BG cognitive loop do?

A

mostly involves caudate

motor learning, planning mvmts ahead of time….but after a mvmt is learned the motor loop (putamen) takes over

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12
Q

Describe the path of the cognitive loop

A

prefrontal cortex > caudate > globus pallidus > VA of thalamus > prefrontal cortex

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13
Q

What does the BG limbic loop do?

A

gives expression to emotions (smiling, gestures, aggression etc)

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14
Q

Describe the path of the limbic loop

A

inferior prefrontal cortex > ventral striatum (aka nucleus accumbens) > ventral pallidum > DMN of thalamus > interior prefrontal cortex

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15
Q

What does the oculomotor loop do?

A

voluntary saccades, disinhibits the superior colliculus

he did not talk about this shit much

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16
Q

is the reticular part of the substantial nigra active or inactive when the eyes are fixed on an object?

A

active

17
Q

What makes up the thalamic fasciculus?

A

ansa lenticularis
lenticular fasciculus

(GP to thalamus)

18
Q

You have a three neuron circuit:

  1. excitatory neuron
  2. inhibitory neuron
  3. spontaneously firing neuron

What happens to neuron 3?

A

it is silenced

19
Q

You have the same three neuron circuit as before, but a new neuron has been added:

  1. excitatory neuron
    2a. inhibitory neuron
    2b. inhibitory neuron
  2. spontaneously firing neuron

What happens to neuron 3?

A

neuron 3 is released and it fires an action potential (disinhibition)

20
Q

Describe the direct pathway of the BG motor loop.

A
  1. Excitatory neurons leave the cerebral cortex and synapse on the striatum
  2. The striatum sends out inhibitory neurons to the globus pallidus internus (GPI)
  3. The GPI sends out inhibitory neurons to the thalamus via the thalamic fasciculus (but ‘less’ inhibitory than usual to the thalamus, because the striatum has inhibited the GPI so it is less active)
  4. The thalamus is disinhibited, so it sends out excitatory neurons to the cortex and increases voluntary movements
21
Q

Does the direct pathway of the motor loop increase or decrease cortical output?

A

increases cortical output (more mvmt)

22
Q

Describe the indirect pathway of the BG motor loop.

A
  1. Excitatory neurons leave the cerebral cortex and synapse on the striatum
  2. The striatum sends out inhibitory neurons to the globus pallidus externa (GPE)
  3. The GPE sends out inhibitory neurons to the subthalamus
  4. The subthalamus sends out excitatory neurons to the GPI
  5. The GPI sends out inhibitory neurons to the thalamus via the thalamic fasciculus. Now the thalamus is inhibited more than usual, because the subthalamus has turned on the GPI more than usual.
  6. Decreased excitatory output from the thalamus to the cortex
  7. Decreased cortical output
23
Q

Does the indirect pathway of the motor loop increase or decrease cortical output?

A

decreases cortical output to suppress unwanted movements

24
Q

What happens if you damage your subthalamus?

A

your indirect pathway will get fucked up so you will have a lot of involuntary movements happening

called hemiballismus

25
Q

Are the putamen and globus pallidus somatotopically arranged?

A

YES

important because the direct pathway can stimulate movement in one are while the indirect pathway can suppress unwanted movements simultaneously in a different area

26
Q

What is the relationship between substantial nigra and the direct motor pathway?

A

striatal projection neurons to the GPI have D1 receptors, which are facilitatory

(i think these receptors help to inhibit GPI more, so the thalamus is less inhibited)

this makes the supplemental motor area active prior to mvmts occurring (who the fuck knows)

27
Q

What is the relationship between substantial nigra and the indirect motor pathway?

A

stratal projection neurons to the GPI have D2 receptors, which are inhibitory

(aka the keep the GPI more turned on so the thalamus is more inhibited)

28
Q

What are the three cardinal features of parkinson’s disease?

A

bradykinesia (slow mvmt)
resting tremor
rigidity

29
Q

What are lewy bodies?

A

found in the substantial nigra, they ‘plug’ dopamine receptors and give you parkinsons booooo

30
Q

What motor pathway is favored in parkinson’s disease and why?

A

the indirect pathway is favored (decreased cortical output — bradykinesia)

this is because the striatum is not receiving any dopamine projections from the compact SN. This causes the striatum to over inhibit the GPE. consequently, the subthalmus is underhibited by the GPE. the subthalamus then overexcites the GPE, causing the thalamus to be over inhibited. decreased thalamic outputs to cortex, decreased movements.

31
Q

How does levodopa work?

A

tries to replace dopamine

32
Q

What is a pallidotomy?

A

possible treatment for parkinsons, you destroy the globus paladus in an attempt to increase cortical outputs and treat bradykinesia

33
Q

What side of the body would a right sided pallidotomy affect?

A

left side of body

LAST NEURO EVER (5 decks)

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